Whenever a creature you control becomes blocked, it gets +1/+1 until end of turn.: Target creature you control gains trample until end of turn. (It can deal excess combat damage to defending player or planeswalker while attacking.)

Somberwald Alpha’s first ability will give each creature you control that becomes blocked +1/+1 until end of turn. It doesn’t matter how many of your opponent’s creatures are blocking each of your creatures.